Xiao Liu PhD Thesis.pdf - Faculty of Information and Communication ...

Thus, the sufficiency property holds.
Here, we also adopt the method of DOMTR (Dynamic Obtaining of Minimum
Time Redundancy) [21]. Based on some initial values which are set up during the
runtime instantiation stage, DOMTR can compute the minimum probability time
redundancy on the fly along scientific workflow execution with minimal
computation. Based on DOMTR, the computation of our checkpoint selection
strategy is basically one or two subtractions or comparisons at each activity covered
by one or more upper bound constraints. Therefore, as proved in [21], the
computation cost is basically negligible.
To conclude, our checkpoint selection strategy strictly ensures that a checkpoint
is selected only when current temporal consistency is below the minimum
acceptable threshold. Meanwhile, since our temporal verification strategy is aware
of the effective probability consistency range and can determine the fine-grained
levels of temporal violations, it also ensures that statistically the time deficit can be
compensated by light-weight temporal violation handling.
6.3 Evaluation
6.3.1 Experimental Settings
The SwinDeW-C simulation environment is introduced in Section 3.5 and hence
omitted here. The experiment settings are as follows. The process definitions are
generated based on the pulsar searching example presented in Section 1.2 and the
attribute settings are based on historic data for the running of scientific workflow
instances [56]. Meanwhile, the experiment settings are extended deliberately for the
purpose of exploring a much larger parameter space to evaluate our strategy in
general software applications of similar nature in distributed high performance
computing environments.
To evaluate the average performance, 10 independent experiments with different
scientific workflow sizes (ranging from 2,000 to 50,000 workflow activities with
their mean activity durations between 30 to 3,000 basic time units 4 ) are executed
4 Here, a basic time unit is used for general evaluation purpose. Specifically, for our pulsar searching
example, a basic time unit here is more or less equal to a second.
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